Installation of heating by induction

ABSTRACT

This invention relates to an induction heating apparatus for the heating of continuously moving tubes of large diameter and great length. The apparatus is made up of a cylindrical inductor having a series of induction spiral turns through which the tubes move. A shield held stationary with respect to the inductor and disposed between the induction turns and the tubes to be heated is provided therefor. This shield is formed of a plurality of sheet-metal plates which are electrically and thermally insulated from one another along the juxtaposed edges thereof. The position of the inductor is made adjustable with respect to the tubes and in relation to the local heat losses therefrom by means of hydraulic jacks. Feeling prongs and temperature sensitive probes are held close to either one of the inductor end supports to detect any variation in the heat distribution across the tubes whereby to obtain a uniform heat distribution there across by varying the inductor position accordingly.

United States Patent 11 1 1111 3,805,010 Cuvelier 1 Apr. 16, 1974 [54]INSTALLATION OF HEATING BY 2,781,437 2/1957 McArthur 219/1079 xINDUCTION [75] Inventor: Michel Charles Cuvelier, Liege,

Belgium [73] Assignee: Elphiac, Brussels, Belgium [22] Filed: Jan. 15,1973 [21] Appl. No.: 323,922

[30] Foreign Application Priority Data Jan. 14, 1972 Belgium 112830 [52]US. Cl. 2l9/l0.77, 219/1079 [51] Int. Cl. H05b 5/06 [58] Field of Search219/10.49, 10.41, 10.43, 219/1069, 10.67, 10.79, 10.77, 10.73

[56] References Cited UNITED STATES PATENTS 3,647,195 3/1972 Drewry263/33 2,848,566 8/1958 Limpel.... 219/1069 X 891,657 6/1908 Berry219/1049 3,317,203 5/1967 Litz et a] 21 /1057 3,489,875 1/1970 Ross219/1079 2,813,959 11/1957 Mitchell et al..... 219/1069 2,969,411 l/l96lGibbs 219/10.79 X

Primary Examiner-Bruce A. Reynolds Attorney, Agent, or Firm-Raymond A.Robic; J. Ernest Kenney; Arthur Schwartz [5 7] ABSTRACT This inventionrelates to an induction heating apparatus for the heating ofcontinuously moving tubes of large diameter and great length. Theapparatus is made up of a cylindrical inductor having a series ofinduction spiral turns through which the tubes move. A shield heldstationary with respect to the inductor and disposed between theinduction turns and the tubes to be heated is provided therefor. Thisshield is formed of a plurality of sheet-metal plates which areelectrically and thermally insulated from one another along thejuxtaposed edges thereof. The position of the inductor is madeadjustable with respect to the tubes and in relation to the local heatlosses therefrom by means of hydraulic jacks. Feeling prongs andtemperature sensitive probes are held close to either one of theinductor end supports to detect any variation in the heat distributionacross the tubes whereby to obtain a uniform heat distribution thereacross by varyingthe inductor position accordingly.

3 Claims, 2 Drawing Figures 1 INSTALLATION OF HEATING BY INDUCTION Thisinvention relates to an induction heating apparams for heatingcontinuously moving tubes or pipes of large diameters and of greatlength, the apparatus comprising a cylindrical inductor through whichthe tubes to be heated move.

The object of the present invention is, on the one hand, to protect theinductor against rapid wear casued, for example, by the heat radiated bythe heated tube and, onthe other hand, to ensure a uniform temperaturethroughout the tube section emerging from the inductor.

The apparatus according to the invention is characterized by theprovision of a shield held stationary with respect to the inductor,between the inductor turns and the tubes to be heated and by theprovision of means for adjusting the position of the inductor inrelation to the local temperature of the tube.

. The invention will now be describedwith reference to a preferredembodiment thereof illustrated in the accompanying drawings in which:

FIG. 1 is a transverse cross-sectional view of the apparatus accordingto this invention, and

FIG. 2 is a longitudinal cross section of an inductor used intheapparatus of the present invention.

A cylindrical inductor is made up of a series of watercooled spiralturns 1, held between an upstream annular support 2 and a downstreamannular support 3 linked together by means of rods 4. The termsupstreamland downstream are meant in relation to the displacement of atube 5 tobe heated and which moves through the cylindrical inductor froman upstream to a downstream direction. The supports 2 and 3 are made ofinsulating material, for example of asbestos plates and reinforced bycement. On the inside of the spiral turns 1 of the inductor, there arefour juxtaposed sheetmetal plates 6,7, 8 and 9, which are pressedagainst strips 10, made of insulating material, by means of clamps 11.and fixed to the supports 2 and 3. The sheetmetal plates are relativelythin so as not to substantially perturb the inductive field. They form aprotective heat shieldfor all the spiral turns 1 of the inductor. Thesheetcmetal plates 6 to 9 are also electrically and thermicallyinsulated from the turns 1 by strips 10. They are likewise insulatedfrom each other owing to an insulating spacing provided between them,along their juxtaposed edges. To avoid buckling of the plates, strips 10are inserted along such spaces which also serve to protect the inductorturns from the heat radiated by the heated tube.

Means for avoiding buckling of the sheet-metal plates 6 to 9 may beprovided. For example, the plates may be crimped or corrugated, or theymay be cooled by a refrigerating fluid such as air, nitrogen, water andthe like. The refigerating fluid may be scavanged or sprinkled on theplates on the side thereof facing the tube to be heated. in this case,appropriate nozzles such as 12 are provided which pass around thedownstream support 3 to direct the refrigerating fluid on the surfacesof the plates 6 to 9 or at least on one of the surfaces of the saidplates.

Cooling'of the plates 6 to 9 may also be performed by forcing therefrigerating fluid through the areas defined by the strips 10, theturns 1 and the plates 6 to 9, or at least some of such areas. For thispurpose, appropriate refrigerating fluid conduits, such as 13, areprovided in the supports 2 and 3 for connecting these areas with afeeding and, eventually, an outlet refrigerating fluid device, notshown.

When the inductor is disposed horizontally, water splashes on the lowerplates are to be feared and to avoid any thermal shock, the plate 6 mustbe cooled. This partial cooling of the shield, made up of the plates 6to 9, may produce an uneven distribution of temperature in the portionof the tube running out of the downstream support 3 of the inductor. Toavoid this drawback and in order to obtain an even temperaturedistribution-across the tube, the inductor is mounted on a cradle 14 theposition of which is adjustable by means of hydraulic jacks 15, forvertical motion, and 16 for horizontal motion. These jacks l5 and 16 areparts of a servo-control system that include an hydraulic liquiddistributor l7 controlled by a temperature probe measuring system, inrelationto the local heat losses in the tube 5 to be heated. If the heatlosses can be determined once and for all, owing to a strong cooling ofthe plate 6, the measuring system may be constituted by feeler prongs 18fixed to one of the supports 2 or 3. In FIG. 2, these prongs 18 aremounted on the upstream support 2. On the other hand, if the heat lossesare liable to vary during heating, the measuring system may beconstituted by probes l9 sensitive to the local temperature of thesurface of tube 5. These'probes are secured on the downstream support 3of the inductor. These probes then give a direct measure of the localtemperature along the cross-section of tube 5 emerging from thedownstream support 3.

The probes 19 or the prongs l8 send out signals useful in theservo-control S(FIG. l toward the liquid .distributors 17. These signalsare transmitted through leads 20. If the probes 19 or the prongs 18 arefour in number they are preferably arranged along two perpendiculardiameters, one vertical, the other horizontal. Thus, the probes 19 orthe prongsl8 disposed along the vertical diameter have a directinfluence on the positioning of jacks 15 for vertical displacement, andthe probes 19 or prongs 18 along thehorizontal diameter directlyinfluence the positioning of the jacks 16 for horizontal displacement.The servo-control system is so designed as to allow the jacks to shiftthe inductor position until the prongs along the same diameter measurethe very same variation from a reference position or until the probes 19along the same diameter measure the very same temperatures. Owing tothis servocontrol system, the parts of the tube surface 5 which endure amore severe loss of heat are submitted to a stronger induction couplingand, hence, to a more intense heating. Thus, a perfectly eventemperature distribution is obtained over the full cross-section of thetube 5 emerging from the downstream support 3.

The servo control system per se does not constitute claimed subjectmatter in this case, and may be constructed, for example, in accordancewith theservo control systems shown in US. Pat. Nos. 2,998,966 and3,647,195. Any conventional temperature responsive servo control systemswhich would provide the desired output function could be used in thisinvention.

I claim:

1. An induction heating apparatus for the heating of continuously movingtubes of large diameter and great length, said apparatus including acylindrical inductor.

having upstream and downstream support means, and further including aseries of induction spiral turns 3 4 shielded with a shield formed of aplurality of sheet temperature and is moved away from the tube metalplates, said tubes moving through said inductor, being heated in thearea of said tube cross section comprising: where said probes sense anincreased local tube a P as a P of the pp of the induetionheattemperature to thereby achieve a uniform heat dismg apparatus, 5tribution across the tube.

a moving mechanism on said cradle on which said inductor is secured andcapable to move said inductor in directions perpendicular to its axis,

a servo-control means for said moving mechanism,

a plurality of heat measuring probes sensitive to the 0 and controllingSaid jacks local temperature of the surface of the tube to be heated,secured near the downstream support of The mducftlowheatmg apparinus asrecned m the inductor Said measuring probes being com claim 1, whereinsaid heat measur ng probes are lonected to Said servo comrol means tooperate Said cated at diametrically opposed POS'IUOI'IIS wth respect tomoving mechanism and displace said inductor in the tube being heated,and wherein said servo-control directions perpendicular to its axis andconse means operates said moving mechanisms to shift the ml to the i f hb to b heated, position of said inductor until said probes sense equal hb id i d t i moved closer t h t b local temperatures at diametricalopposite portions of being heated in the area of said tube cross sectionsaid tube surface. where said probes sense a decreased local tube 2. Theinduction heating apparatus recited in claim 1, wherein said mechanismcomprises hydraulic jacks and wherein said servo-control means comprisehydraulic fluid feeding and controlling means for feeding

1. An induction heating apparatus for the heating of continuously movingtubes of large diameter and great length, said apparatus including acylindrical inductor having upstream and downstream support means, andfurther including a series of induction spiral turns shielded with ashield formed of a plurality of sheet metal plates, said tubes movingthrough said inductor, comprising: a cradle as a part of the support ofthe induction heating apparatus, a moving mechanism on said cradle onwhich said inductor is secured and capable to move said inductor indirections perpendicular to its axis, a servo-control means for saidmoving mechanism, a plurality of heat measuring probes sensitive to thelocal temperature of the surface of the tube to be heated, secured nearthe downstream support of the inductor, said measuring probes beingconnected to said servo-control means to operate said moving mechanismand displace said inductor in directions perpendicular to its axis andconsequently to the axis of the tube to be heated, whereby said inductoris moved closer to the tube being heated in the area of said tube crosssection where said probes sense a decreased local tube temperature andis moved away from the tube being heated in the area of said tube crosssection where said probes sense an increased local tube temperature tothereby achieve a uniform heat distribution across the tube.
 2. Theinduction heating apparatus recited in claim 1, wherein said mechanismcomprises hydraulic jacks and wherein said servo-control means comprisehydraulic fluid feeding and controlling means for feeding andcontrolling said jacks.
 3. The induction heating apparatus as recited inclaim 1, wherein said heat measuring probes are located at diametricallyopposed positions wth respect to the tube being heated, and wherein saidservo-control means operates said moving mechanisms to shift theposition of said inductor until said probes sense equal localtemperatures at diametrical opposite portions of said tube surface.